The invention relates to the art of automatic fastening machines, and more particularly to an inspection assembly which ensures that a hole in a workpiece has been drilled or otherwise formed to specification and is also properly positioned.
One area of use of the present invention is in automatic drilling and riveting machines wherein a drill forms a hole in two metal worksheets to be joined. A fastener, such as a rivet, is then inserted into the hole and upset to join .the worksheets. However, before the inserting and upsetting operations, it is beneficial to know that the hole conforms to predetermined specifications. A probe according to the present invention is thus moved along a work centerline corresponding to the hole center axis and introduced into the hole. Capacitance plates mounted around the periphery of the probe measure the hole size and degree of roundness. Furthermore, an undersized hole can be measured for subsequent operations such as cold working, reaming and countersinking whereupon the hole can be measured again for size and quality. These measurements can be recorded and plotted to determine trends as, for example, to indicate when a drill bft is wearing and needs replacing. In addition, measurements can be made of selected depths in the hole, and variable stack thicknesses of workpieces can be accommodated. The probe can be accurately positioned axially along the center axis to measure a targeted portion of the hole, such as a portion below a countersink. Furthermore, the probe can be used to insure that the hole position is at a desired location in the worksheets.